Synchronizing mechanism

ABSTRACT

An office chair has a base support, a seat support and a backrest support. A synchronizing mechanism for a correlated seat/backrest movement has the seat support articulated directly on a first pivot bearing of the base support, the backrest support articulated directly on a second pivot bearing of the base support, and the backrest support connected to the seat support via an articulation. The articulation axis of the articulation, as seen in the longitudinal direction of the seat, is in front of the pivot axis of the second pivot bearing, such that a pivoting movement of the backrest to the rear about the pivot axis of the second pivot bearing induces a rotation of the seat support about the pivot axis of the first pivot bearing and thus a lifting movement of just the front region of the seat support.

The invention relates to a synchronizing mechanism for a correlated seat/backrest movement of an office chair, having a base support which is placeable on a chair column, a seat support and a backrest support.

The term “synchronizing mechanism” is understood to mean assemblies in the seat substructure of an office chair which ensure coupled kinematics which result in a particular relative movement of the seat and backrest with respect to one another. The office-chair seat, which is generally provided with an upholstered seat surface, is fitted on the seat support. The backrest support, which commonly extends rearwardly from the actual synchronizing mechanism, supports the backrest of the office chair on an upwardly extending extension arm. The seat support and the backrest support are usually coupled together in an articulated manner such that a rearward pivoting movement of the backrest—as can be brought about for example when the chair user leans against the backrest—induces a lowering movement of the rear edge of the seat in the downward direction.

In order to be able to use the chair easily, it is advantageous if the pivoting resistance of the backrest can be set depending on the weight of the user. In order to change the pivoting resistance of the backrest, such synchronizing mechanisms usually have a more or less complicated spring arrangement for preloading the synchronizing mechanism.

It is an object of the present invention to provide a synchronizing mechanism which has a particularly simple structure and is therefore producible in a cost-effective manner and nevertheless provides the ease of use of a conventional synchronizing mechanism. In particular, the synchronizing mechanism is intended to have no or only a few or weak spring elements.

This object is achieved by a synchronizing mechanism as claimed in claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

According to the invention, it is provided that the seat support is connected in an articulated manner directly, i.e. without the use of a coupling element such as a link or the like, to the base support, wherein at the same time the backrest support, which is connected directly to the base support, and specifically is pivotable about a transverse axis on the base support, is connected in an articulated manner to the seat support such that a rearward pivoting movement of the backrest induces a lifting movement of the front region of the seat support.

A basic idea of the invention is that the user of the office chair lifts himself in the upward direction by applying load to the backrest itself. In other words, when actuating the synchronizing mechanism by pushing back the backrest, the user acts against his own weight resting on the seat. The desired pivoting resistance is thus set effectively automatically on account of the weight of the user. Spring arrangements, known from the prior art, for setting the pivoting resistance (for example in the form of a plurality of compression or tension springs connected in parallel) and complicated setting mechanisms (worm gears, gear wheels, threaded rods etc.) are not necessary. As a result, the production costs of the synchronizing mechanism are considerably reduced. At the same time the failure safety is increased.

The lever geometry necessary for the “self-setting” mechanism of the present invention is achieved in that the pivot axis of the connection of the backrest support to the base support, as seen in the longitudinal direction of the seat, is arranged behind the articulation axis of the connection of the backrest support to the seat support.

The number of components and thus the production costs are particularly low because both the backrest support and the seat support are connected in an articulated manner directly, i.e. without interposition of an additional component, to the base support.

On account of the structural arrangement of the components, when the backrest is pivoted, the front region of the seat support is lifted. In this case, the distance between the front region of the seat support and the base support is increased, while the rear region of the seat support remains firmly connected to the base support. Thus, the seat is inclined rearwardly about the pivot axis of the seat support/base support connection in a defined relationship with the movement of the backrest. This produces the desired synchronizing effect, in the case of which the angle of the seat support with respect to the backrest support changes.

The weight of the user has a direct effect on the pivoting resistance perceptible by the user. A light user has to overcome a much lower pivoting resistance than a heavy user, during pivoting. Subjectively, every user “feels” the same resistance during the pivoting of the backrest. On account of the arrangement of the pivot bearings and articulations and the configuration thereof, the synchronizing movement of the seat support can be adapted individually to the requirements placed on the chair. Thus, for example, by changing the distance between the pivot bearings or articulations, it is possible to set how much the seat support is inclined when the backrest is pivoted.

Compared with the solutions known from the prior art, according to the invention, a structurally comparatively simple pivoting mechanism is provided, in the case of which the “shirt pulling effect”, as it is known, is considerably reduced. In other words, particularly high sitting comfort is achieved without it being necessary to resort to relatively complicated and expensive solutions.

Compared with other already known “self-setting” mechanisms, the present synchronizing mechanism is distinguished by the fact that it has a particularly flat construction, and so a corresponding assembly only requires very little installation space. At the same time, the mechanism has an extremely simple structure. The desired synchronizing movement can be brought about by way of the three known components of backrest support, base support and seat support, which are connected together with the aid of only three articulation points.

An exemplary embodiment of the invention is explained in the following text with reference to the drawings, in which:

FIG. 1 shows a side view of the synchronizing mechanism in the basic position, and

FIG. 2 shows a side view of the synchronizing mechanism in a position pivoted rearwardly.

Both of the figures show the synchronizing mechanism purely in a schematic manner and with the constituent parts which are essential for the invention. Identical reference signs correspond in this case to elements having the same or a similar function.

The synchronizing mechanism has a base support 1 which is positioned, by way of a conical mount 2, on the upper end of a chair column (not depicted). Furthermore, the synchronizing mechanism comprises a substantially frame-like seat support 3 and a backrest support 4, which is fork-like in plan view and the side pieces 5 of which are arranged on both sides of the base support 1. The seat support 3 is provided in order for a preferably upholstered seat surface (not depicted) to be accommodated or mounted thereon. The mounting takes place in a conventional manner with the aid of fastening elements (not illustrated specifically). A backrest (not illustrated specifically), which is height-adjustable in the case of modern office chairs, is attached to the backrest support 4. The backrest can also be connected integrally to the backrest support 4.

The entire synchronizing mechanism is constructed in a mirror-symmetrical manner with regard to the center longitudinal plane, as far as the actual kinematics are concerned. To this extent, it is assumed, in the following description, that structural elements of the actual pivoting mechanism are always present in pairs, on both sides.

FIG. 1 shows the basic position in which the seat support 3 is arranged in a substantially horizontal manner. FIG. 2 shows the synchronizing mechanism in a rearwardly pivoted position of the backrest support 4. The front region of the seat support 3 is in this case lifted.

The rear region 25 of the seat support 3 is articulated directly on the base support, specifically with the aid of a bearing pin 6 on a first pivot bearing 27 of the base support 1. The seat support 3 can thus be pivoted about a transversely located pivot axis 13. In order to form the pivot bearing 27 in the region of the base support 1, first mounting limbs 12 of the seat support 3 extend downwardly from the support plate 11 of the seat support 3 in the direction of the base support 1.

Since the pivot bearing 27 is arranged at the rear end 9 of the base support 1, seat supports 3 and/or seats which project beyond the rear edge of the base support 1 can also be pivoted in an undisrupted manner, without this requiring particular and complicated design measures.

The backrest support 4 is articulated directly on a second pivot bearing 28 of the base support 1 by way of a side piece 5 extending in the direction of the front edge 8 of the seat, with the aid of a bearing pin 6. The backrest support 4 can thus be moved about a transversely located pivot axis 15 from the basic position into a rearwardly pivoted position. The second pivot bearing 28 is located, as seen in the longitudinal direction 14 of the seat, approximately in the center of the base support 1, specifically directly in front of the conical mount 2.

Furthermore, the backrest support 4 is also directly connected in an articulated manner to the seat support 3, more precisely by way of second mounting limbs 19 of the seat support 3, which extend downwardly in the direction of the base support 1 from the support plate 11 of the seat support 3. A slot 20 arranged in the second mounting limbs 19 forms a rotary sliding articulation 16 together with a pin 10 fastened to the front end of the side piece 5 of the backrest support 4. The backrest support 4 and seat support 3 are thus pivotable about a transversely located articulation axis 22 and at the same time connected together in a movable manner in the longitudinal direction 14 of the seat. In other words, in addition to a rotary movement, a translatory movement of the articulation 16 is also possible at the same time. This is necessary in order to prevent the seat support 3 being blocked, because the path of movement of the backrest support 4 about the second pivot axis 15 deviates from the path of movement of the seat support 3 about the first pivot axis 13.

The second pivot axis 15 defined by the articulation of the backrest support 4 on the base support 1 is, as seen in the longitudinal direction 14 of the seat, arranged behind the articulation axis 22 defined by the articulation of the backrest support 4 on the seat support 3, such that a rearward pivoting movement of the backrest in the pivoting direction 7 about the pivot axis 15 of the second pivot bearing 28 induces a rotation of the seat support 3 about the pivot axis 13 of the first pivot bearing 27 and thus a lifting movement 23 just of the front region 26 of the seat support 3. The rear region 25 of the seat support 3 is not lifted. A seat part (not illustrated) located behind the pivot axis 13 is lowered.

In other words, as a result of the backrest being pivoted rearwardly and downwardly, the seat support 3 is entrained in the pivoting direction 7 and, on account of the lever arrangement formed by the side piece 5 of the backrest support 4, lifted. The positions of the articulation points 15, 22 of the backrest support 4 on the base support 1 on the one hand and on the seat support 3 on the other hand define, according to the invention, a lever element as an integral constituent part of the front region of the side piece 5 of the backrest support 4.

The distances between the first pivot axis 13 and the second pivot axis 15 and between the second pivot axis 15 and the articulation axis 22 define the synchronism ratio of the mechanism, i.e. the transmission ratio of the backrest support pivot angle 29 to the seat support pivot angle 30. The selected arrangement of axes determines the lever geometry of the mechanism and defines the manner in which the seat support 3 is lifted and moved synchronously with the pivoted backrest.

In the embodiment illustrated in the figures, in the non-pivoted basic position, the first pivot axis 13 and the articulation axis 22 are located substantially at one height, while the second pivot axis 15 is arranged only a little higher. The distance 17 in the example is only 2 mm. This produces, inter alia, a very flat construction.

In a particularly advantageous embodiment, the distance 31 from the first pivot axis 13 to the second pivot axis 15 is 107 mm and the distance 32 from the first pivot axis 13 to the articulation axis 22 is 137 mm. Even in a position in which the synchronizing mechanism is pivoted rearwardly to the maximum extent, there is no change in the order in which the axes 13, 15, 22 are arranged.

As a result of an arrangement of the first pivot axis 13 at the rear end 9 of the base support 1, a comparatively large distance 31, 32 from the second pivot axis 15 or from the articulation axis 22 can be produced in a structurally particularly simple manner, this resulting in a particularly advantageous synchronism ratio in which, when the backrest support 4 is pivoted a long way rearwardly, the front edge 8 of the seat support 3 is lifted only a little. The embodiment in which the inclination 30 of the seat support 3 with respect to the horizontal starting position is about 5.5° when the backrest support 4 is pivoted 29 downwardly about 25° has proved to be particularly advantageous. In the pivoted state, the vertical distance 33 between the second pivot axis 15 and the articulation axis 22 is 11 mm in the example depicted in FIG. 2.

The position of the axes 13, 15, 22 has the effect that the overall pivot point of the mechanism at the start of the pivoting movement of the backrest corresponds virtually with the actual pivot point of the chair user. This results in a particularly comfortable movement sequence and the occurrence of negative effects, such as, for example, the shirt pulling effect, as it is known, can be avoided.

In the present case an approximately linear mechanism characteristic curve is achieved, in which the pivoting resistance is approximately constant over the entire movement sequence. In this case, the seat support 3 is lifted only in the front region 26, as a result of which the intuitive human movement sequence is supported during rearward pivoting.

The pivoting mechanism described ensures that the backrest support 4 can be pivoted with the backrest about a pivot axis, in this case the second pivot axis 15, in the pivoting direction 7. At the same time, the rearward pivoting movement of the backrest induces a lifting movement 23 of the front region 26 of the seat support 3. During rearward and downward pivoting of the backrest, no forward or rearward movement of the seat support 3 in the longitudinal direction 14 of the seat takes place. The seat support 3 only executes a pivoting movement about the first pivot axis 13, while the base support 1 remains with its two pivot bearings 27, 28 in a fixed position.

In order to support or influence the pivoting resistance and to prevent the backrest from tipping rearwardly in an uncontrolled manner, and also to return the backrest securely from the pivoted position into the basic position as soon as the user is no longer applying load to the backrest, use is made of a spring arrangement having one or more spring elements. For example, this is a spring 21, arranged in the region of the front base support 18, which is supported on the one hand on the base support 1 and on the other hand on the side piece 5 of the backrest support 4, and which is loaded during pivoting of the backrest support 4. The spring element 21 needs to be configured only to be comparatively weak, such that only small spring forces act overall on the components of the mechanism, this resulting in much less stressing of the components compared with conventional mechanisms.

The embodiment depicted in FIGS. 1 and 2, in which

a) the backrest support 4 is connected to the base support 1 only via a single direct connection in the form of a pivot bearing 28, b) the backrest support 4 is connected to the seat support 3 only via a single direct connection in the form of an articulation 16, and c) the seat support 3 is connected to the base support 1 only via a single direct connection, specifically a further pivot bearing 13, and via an indirect connection, wherein the indirect connection is established by the backrest support 4 which is connected on the one hand to the seat support 3 via the articulation 16 and on the other hand to the base support 1 via the pivot bearing 15, is particularly advantageous because the desired synchronous movement can be realized thereby with particularly few components. Alternatively, it is also possible, however, to use, instead of the articulation 16 integrated in the backrest support 4 for attaching the backrest support 4 to the seat support 3, one or more coupling elements which are articulated on the one hand to the backrest support 4 and on the other hand to the seat support 3. As a result, the number of axes would rise to four, with the result that further possibilities for configuring the synchronous movement are produced. At the same time, however, the basic construction of the mechanism with the above-mentioned features, in particular relating to the lever principle and the manner in which the seat support 3 moves, would be retained.

All of the features illustrated in the description, the following claims and the drawings may be essential to the invention both individually and in any desired combination with one another.

LIST OF REFERENCE SIGNS

-   -   1 Base support     -   2 Conical mount     -   3 Seat support     -   4 Backrest support     -   5 Side piece     -   6 Bearing pin     -   7 Pivoting direction     -   8 Front edge of the seat     -   9 Rear end of the base support     -   10 Pin     -   11 Support plate     -   12 First mounting limb     -   13 First pivot axis     -   14 Longitudinal direction of the seat     -   15 Second pivot axis     -   16 Rotary sliding articulation     -   17 Distance     -   18 Front end of the base support     -   19 Second mounting limb     -   20 Slot     -   21 Spring     -   22 Articulation axis     -   23 Lifting movement     -   24 (unused)     -   25 Rear region of the seat support     -   26 Front region of the seat support     -   27 First pivot bearing     -   28 Second pivot bearing     -   29 Pivot angle of the backrest support     -   30 Pivot angle of the seat support     -   31 Distance     -   32 Distance 

1-4. (canceled)
 5. A synchronizing mechanism for a correlated seat/backrest movement of an office chair, the chair having a base support to be placed on a chair column, a seat support and a backrest support, the synchronizing mechanism comprising: a first pivot bearing disposed on the base support, said first pivot bearing having a first pivot axis and directly articulating the seat support; a second pivot bearing disposed on said base support, said second pivot bearing having a second pivot axis and directly articulating the backrest support; an articulation connecting the backrest support to the seat support; and said articulation having an articulation axis disposed, as seen in a longitudinal direction of the seat support, in front of said second pivot axis of said second pivot bearing, such that a pivoting movement of the backrest to a rear about said second pivot axis induces a rotation of the seat support about said first pivot axis of said first pivot bearing and a lifting movement of a forward region of the seat support.
 6. The synchronizing mechanism according to claim 5, wherein said articulation connects the backrest support directly to the seat support.
 7. The synchronizing mechanism according to claim 5, wherein said articulation is a rotary sliding articulation.
 8. The synchronizing mechanism according to claim 5, wherein said first pivot bearing is disposed at a rear end of the base support.
 9. An office chair with a synchronizing mechanism for a correlated seat/backrest movement, the office chair comprising: a base support to be placed on a chair column, a seat support and a backrest support; wherein said seat support is articulated directly on a first pivot bearing of said base support; wherein said backrest support is articulated directly on a second pivot bearing of said base support; an articulation connecting said backrest support to said seat support, said articulation having an articulation axis disposed in front of said pivot axis of said second pivot bearing, in a longitudinal direction of said seat support, such that a rearward pivoting movement of said backrest about said pivot axis of the second pivot bearing induces a rotation of said seat support about said pivot axis of said first pivot bearing with a lifting movement of a forward region of said seat support. 